Periodicity

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Foundation Chemistry UNIT 1

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SUPER ADJECTIVES:

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Periodicity

Chemical Properties

Discuss the changes in nature, from ionic to covalent and from basic to acidic, of the oxides across Period 3

Look at link 3.3.2

Elements on the left are metallic, right are non-metals, Al is a metalloid (semi-metal).

Discuss the similarities and differences in the chemical properties of elements in the same group

Look at link 3.3.1

Reactions of elements in the same group are similar because they have identical outer shells

Largely determined by the number of electrons in the valence shell of an element

Physical Properties

Compare the relative electronegativity values of two or more elements based on their positions in the Periodic Table

Na --> Ar (across period 3):

Electronegativity increases due to increased nuclear charge --> greater attraction for electrons.

Ionisation energy increases due to increased nuclear charge.

Ionic radius decreases Na --> Al (due to increased nuclear charge) jumps Al --> Si (due to reversal of ionisation direction...increased electron-electron repulsion) decreases Si --> Ar (due to increased nuclear charge).

Atomic radius decreases due to increased nuclear charge --> greater attraction for electrons.

F --> I (Down the halogens):

Electronegativity decreases due to increased shielding -> decreased attraction for outer electrons.

Melting/boiling point increases due to increased number of electrons->increased london dispersion forces.

Ionic radius increases due to increased electron shielding.

Atomic radius increases due to increased electron shielding.

Li --> Cs (down the alkali metals)

Electronegativity decreases due to increased shielding --> decreased attraction for outer electrons.

Melting/boiling point decreases due to increased electron shielding --> decreased forces.

Ionisation energy decreases due to increased electron shielding.

Atomic radius increases due to increased electron shielding. Ionic radius increases due to increased electron shielding.

Electronegativity is the ability of an atom to attract electrons in a covalent bond

Sheilding is where an electron is sheilded from the full attrcation of the nucleus

The effective nuclear charge felt by an atom's valence electrons increases with the group number of the element. it increases across a period but stays approximately the same down the group

The fiirst ionization energy of an element is the energy required to remove one mole of electrons fron on mole of gaseous atoms.electronegativity

Trends across Period 3

Describe the reactions of chlorine and the chlorides referred to in 13.1.1 with water

Explain the physical states (under standard conditions) and electrical conductivity (in molten state) of the chlorides and oxides of the elements in Period 3 in terms of their bonding and structure

The Periodic Table

The number of electrons in the valence shell gives an element its group number

The period refers to the number of energy levels occupied and the group, to the number of electrons in the valence shell

The rows are the periods and the columns are the groups

Elements are placed in order of increasing atomic no. (Z)

First-row d-block Elements

Outline the econimic significance of catalysts in the Contact and Haber processes

State examples of the catalytic action of transition elements and their compounds

Explain why some complexes of d-block elements are coloured

Define the term ligand

Describe and explain the formation of complexes of d-block elements

Explain the existence of variable oxidation number in ions of transition elements

Explain why Sc and Zn are not considered to be transition elements

List the characteristic properties of transition elements